The invention relates to a paint drying system for painted bodies, especially automobiles and particularly, but not exclusively, a system for drying painted motor cars.
Conventional automobile spraybooths dry solvent-borne paints which have been applied onto the surfaces of an automobile by passing heated air over the painted surface. Typically, heated air is blown down through inlets in a ceiling of the booth and is evacuated through floor outlets. This process involves the release of polluting solvents into the atmosphere after the paint has dried. In an effort to conform with new legislation which regulates the use of solvent-borne paints, paint manufacturers have developed new paints, such as water-borne paints which are less damaging to the environment.
However, the conventional paint drying spraybooth has proved unsuitable for the drying of water-borne paints. This is because it relies on the volatility of the paint solvent to dry the paint quickly. As water is not volatile it takes substantially longer to evaporate under normal ambient conditions. The water in water-borne paints is thereby released more slowly, resulting in extended drying times when using conventional drying systems. The drying of water-borne paints is further hindered when ambient humidity levels rise. Experiments involving dehumidification techniques have proved impractical and expensive.
It is also known, as described in EP 0 690 279, to dry water-borne paints with directional air jets using re-circulated air from within the spraybooth. As described in this specification, the jets are directly optically aligned with individual painted surfaces to be dried. The specification states that the directional air jets, when used with heat lamps, reduce the drying times for one vehicle from 60 minutes to 8-14 minutes. This is still significantly longer than is required for the drying of solvent-borne paints. Furthermore, since the air jets are individually aimed directly at painted surfaces, water may be entrained in the paint resulting in subsequent blistering of the paint surface.